Construction of Discrete Pentanuclear Platinum(II) Stacks with Extended Metal-Metal Interactions by Using Phosphorescent Platinum(II) Tweezers

Manipulation of 1D and 2D self-assembly via geometry modulation of adamantane isocyanide Pt(II) complexes

Two cationic luminescent cyclometalated Pt(II) complexes with adamantane-based isocyanide ligands are reported. This work provides important insights for the manipulation of the 1D and 2D self-assembly of Pt(II) complexes by controlling the geometry.

Heavy-Metal Ions Removal and Iodine Capture by Terpyridine Covalent Organic Frameworks

Porous materials are excellent candidates for water remediation in environmental issues. However, it is still a key challenge to design efficient adsorbents for rapid water purification from various heavy metal ions-contaminated wastewater in one step. Here, two robust nitrogen-rich covalent organic frameworks (COFs) bearing terpyridine units on the pore walls by a "bottom-up" strategy are reported. Benefitting from the strong chelation interaction between the terpyridine units and various heavy metal ions, these two terpyridine COFs show excellent removal efficiency and capability for Pb2+, Hg2+, Cu2+, Ag+, Cd2+, Ni2+, and Cr3+ from water. These COFs are shown to remove such heavy metal ions with >90% of contents at one time after the aqueous metal ions mixture is passed through the COF filter. The nitrogen-rich features of the COFs also endow them with the capability of capturing iodine vapors, offering the terpyridine COFs the potential for environmental remediation applications.

Enhanced Near-infrared Phosphorescent Emission Modulated by Clipping of Metallotweezers in Aqueous Media

Near-infrared phosphorescent materials have received significant attention due to their potential applications in bioimaging and diagnostics. Although, many types of organic phosphors with near-infrared emission have been developed, the low phosphorescence efficiency in aqueous solution hampers their practical applications in biological systems. Hence, there is an urgent need to develop near-infrared phosphorescent materials with high emission efficiency in aqueous media. Metallotweezers, based on d8 transition metal complexes, emerge as the potential candidates for realizing this objective. Specifically, metallotweezers, featuring two positively charged platinum(II) terpyridine and neutral gold(III) diphenylpyridine pincers on diphenylpyridine spacer, have been designed and synthesized, respectively. The pre-organization effect, rendered by the rigid spacer, enables the resulting metallotweezers to complex with each other, resulting in the formation of clipping complex. The synergistic rigidifying and shielding effects of clipping structure results in enhanced phosphorescent emission intensity. Concurrently, due to phase segregation between the clipping units and the polyethylene glycol tail, the clipping complex undergoes self-assembly in aqueous solution, resulting in phosphorescent emission in the near-infrared region. Overall, non-covalent clipping of metallotweezers illustrated in this study presents a new and effective approach toward near-infrared phosphorescent materials.

Achieving Circularly Polarized Phosphorescence through Noncovalent Clipping of Metallotweezers

Circularly polarized phosphorescent materials, based on host-guest complexation, have received significant attention due to their outstanding emission performance in solutions. Recent studies have primarily focused on macrocyclic host-guest complexes. To broaden the scope of this research, there is a keen pursuit of developing novel chiral phosphorescent host-guest systems. Metallotweezers with square-planar d8 transition metal complexes emerge as promising candidates for achieving this objective. Specifically, metallotweezers, comprising platinum(II) terpyridine and gold(III) diphenylpyridine pincers on a diphenylpyridine scaffold, have been designed and synthesized. Due to the preorganization effect rendered by the diphenylpyridine scaffold, the resulting metallotweezers are capable of complexing with each other and forming quadruple stacking structures. The phosphorescent emission is enhanced owing to the synergistic rigidifying and shielding effects. Meanwhile, the steric effect of chiral (1R) pinene units on the platinum(II) terpyridine pincers results in a stereospecific twist for the quadruple stacking structures. Thus, the chirality transfers from the molecular to the supramolecular level. By a combination of phosphorescent enhancement and supramolecular chirality for the clipping complex, circularly polarized phosphorescent emission is achieved. Overall, noncovalent clipping of metallotweezers exemplified in the current study presents a novel and effective approach toward solution-processable circularly polarized phosphorescent materials.

Synthesis, Characterization, and Resistive Memory Behaviors of Highly Strained Cyclometalated Platinum(II) Nanohoops

Strained carbon nanohoops exhibit attractive photophysical properties due to their unique π-conjugated structure. However, incorporation of such nanohoops into the pincer ligand of metal complexes has rarely been explored. Herein, a new family of highly strained cyclometalated platinum(II) nanohoops has been synthesized and characterized. Strain-promoted C-H bond activation has been observed during the metal coordination process, and Hückel-Möbius topology and random-columnar packing in the solid state are found. Transient absorption spectroscopy revealed the size-dependent excited state properties of the nanohoops. Moreover, the nanohoops have been successfully employed as active materials in the fabrication of solution-processable resistive memory devices, including the use of the smallest platinum(II) nanohoop for the fabrication of a binary memory, with low switching threshold voltages of ca. 1.5 V, high ON/OFF current ratios, and good stability. These results demonstrate that strain incorporation into the structure can be an effective strategy to fundamentally fine-tune the reactivity, optoelectronic, and resistive memory properties.

Unusually short unsupported Au(III)⋯Au(III) aurophilic contacts in emissive lanthanide tetracyanoaurate(III) complexes

A series of [Au(CN)4]- salts with lanthanide 2,2'-bipyridine dioxide cations features Au(III) aurophilic interactions between [Au(CN)4]- groups, with Au⋯Au distances of 3.3603(4) Å and 3.4354(4) Å that are shorter than any previously reported. Computations predict the interactions to be weakly attractive; packing effects appear to also contribute to the close contacts. The materials are emissive: there is no Au(III)-based luminescence, but for Ln = Eu the PLQY of 29% is surprisingly high compared to related analogues.

Assembling Molecular Clips To Build π-Stacks

Nature utilizes an intimate stacking of aromatic motifs to construct functional structures, as demonstrated in protein folding and polynucleotide assembly. However, organized π-stacks of artificial molecules are difficult to build, primarily due to the weak, non-directional, and context-sensitive nature of van der Waals forces. To overcome these challenges, chemists have invented ingenious architectural designs to construct π-stacked supramolecular assemblies using clip-like molecules. This Concept article focuses on molecular clips that enable precise spatial control over assembly patterns, beyond the scope of simple host-guest chemistry. Different design strategies are analyzed and compared that leverage non-covalent interactions to create multi-layer π-stacks. Particular emphasis is placed on the choice of spine units as they play a crucial role in controlling the (i) spacing, (ii) orientation, and (iii) conformational pre-organization of linked aromatics to achieve long-range spatial ordering.

Stoichiometric Control of Guest Recognition of Self-Assembled Palladium(II)-Based Supramolecular Architectures

We report flexible [Pd(L)2 ]2+ complexes where there is self-recognition, driven by π-π interactions between electron-rich aromatic arms and the cationic regions they are tethered to. This self-recognition hampers the association of these molecules with aromatic molecular targets in solution. In one case, this complex can be reversibly converted to an 'open' [Pd2 (L)2 ]4+ macrocycle through introduction of more metal ion. This is accomplished by the ligand having two bidentate binding sites: a 2-pyridyl-1,2,3-triazole site, and a bis-1,2,3-triazole site. Due to favourable hydrogen bonding, the 2-pyridyl-1,2,3-triazole units reliably coordinate in the [Pd(L)2 ]2+ complex to control speciation: a second equivalent of Pd(II) is required to enforce coordination to bis-triazole sites and form the macrocycle. The macrocycle interacts with a molecular substrate with higher affinity. In this fashion we are able to use stoichiometry to reversibly switch between two different species and regulate guest binding.

Molecular Tetris by sequence-specific stacking of hydrogen bonding molecular clips

A face-to-face stacking of aromatic rings is an effective non-covalent strategy to build functional architectures, as elegantly exemplified with protein folding and polynucleotide assembly. However, weak, non-directional, and context-sensitive van der Waals forces pose a significant challenge if one wishes to construct well-organized π-stacks outside the confines of the biological matrix. To meet this design challenge, we have devised a rigid polycyclic template to create a non-collapsible void between two parallel oriented π-faces. In solution, these shape-persistent aromatic clips self-dimerize to form quadruple π-stacks, the thermodynamic stability of which is enhanced by self-complementary N-H···N hydrogen bonds, and finely regulated by the regioisomerism of the π-canopy unit. With assistance from sufficient electrostatic polarization of the π-surface and bifurcated hydrogen bonds, a small polyheterocyclic guest can effectively compete against the self-dimerization of the host to afford a triple π-stack inclusion complex. A combination of solution spectroscopic, X-ray crystallographic, and computational studies aided a detailed understanding of this cooperative vs competitive process to afford layered aromatics with extraordinary structural regularity and fidelity.

The New Di-Gold Metallotweezer Based on an Alkynylpyridine System

We developed a simple method to prepare one gold-based metallotweezer with two planar Au-pyrene-NHC arms bound by a 2,6-bis(3-ethynyl-5-tert-butylphenyl)pyridine unit. This metallotweezer is able to bind a series of polycyclic aromatic hydrocarbons through the π-stacking interactions between the polyaromatic guests and the pyrene moieties of the NHC ligands. The metallotweezer was also used as a host for the encapsulation of planar metal complexes, such as the Au(III) complex [Au(C^N^C)(C≡CC₆H₄-OCH₃-p)], for which there is a large binding constant of 946 M⁻¹.

Phosphorescent Host-Guest Complexes on the Basis of Polyhedral Oligomeric Silsesquioxane-Functionalized Metallotweezers

Phosphorescent host-guest systems have attracted considerable attention because of their intriguing properties and diverse applications. In this study, a polyhedral oligomeric silsesquioxane-functionalized gold(III) tweezer receptor has been designed and synthesized. It is capable of sandwiching platinum(II) terpyridine compounds into its cavity with a high noncovalent binding affinity (association constants: ∼10⁵ M^-1 in chloroform). The resulting heterometallic host-guest complexes exhibit enhanced phosphorescent emission compared with those of the individual species in chloroform, thanks to the prevention of vibration and rotation upon noncovalent complexation. They can further assemble into nanospheres in chloroform/diethyl ether (1:9, v/v) owing to phase segregation between the metallotweezer/guest motif and the peripheral polyhedral oligomeric silsesquioxane unit. When terpyridine platinum(II) chloride serves as the complementary guest, the resulting noncovalent system displays an intraligand emission at the individual host-guest complexed state yet excimeric emission at the supramolecular assembled state, yielding the phosphorescent solvatochromic behaviors. Overall, the polyhedral oligomeric silsesquioxane-functionalized metallotweezer combines guest encapsulation and supramolecular assembly capabilities, which provides new avenues for color-tunable phosphorescent materials.

A Catalogue of Orthogonal Complementary Ligand Pairings for Palladium(II) Complexes

Molecular recognition is a form of information transfer, seen in the base pairing in DNA which is derived from the identity (acceptor or donor) and number of hydrogen bond sites within each base. Here we report bis‐ligand palladium(II) complexes that exhibit similar complementarity. Pd(II) has square planar four‐coordinate geometry, giving control over ligand orientation and denticity. Pairings were developed using ligand denticity (3 : 1 or 2 : 2), and hydrogen bond capability (AA:DD or AD:DA) or lack thereof. Five pairings were investigated, with two sets of four being found fully orthogonal. The two 3 : 1 pairings exhibited limited ligand exchange. The extent of this exchange varied dependant on solvent from 2 : 1 (desired to undesired) to 6 : 1. A reliable and varied set of ligand pairs have therefore been developed for bis‐ligand coordination sphere engineering in pursuit of sorting for complex molecular architectures and molecular‐level information storage and transfer events.

Molecular Alignment of Alkynylplatinum(II) 2,6-Bis(benzimidazol-2-yl)pyridine Double Complex Salts and the Formation of Well-Ordered Nanostructures Directed by Pt···Pt and Donor-Acceptor Interactions

A new class of alkynylplatinum(II) bzimpy (bzimpy = bis(benzimidazol-2-yl)pyridine) double complex salts (DCSs) containing dialkoxynaphthalene or pyromellitic diimide moieties on the alkynyl ligand has been reported to display distinct morphological properties compared to their precursor alkynylplatinum(II) complexes, with the capability of being aligned by the directional Pt···Pt and/or π-π stacking interactions. The incorporation of donor and acceptor units on the alkynyl ligands has been found to significantly perturb the alignment of the oppositely charged complex ions in the DCSs to stack in a twisted head-to-head manner, attributed to the additional driving forces of electrostatic and donor-acceptor interactions. The modulation of the Pt···Pt distances and the extent of aggregate formation have been demonstrated by altering the charge matching between the platinum(II) bzimpy moieties and the donor or acceptor moieties on the alkynyl ligand.

Metalation of a gold(I) metalloligand with P,C-bridging phosphinoferrocenyl groups enables construction of defined multimetallic arrays

The reactions of gold(I) metalloligand [Au2{µ(P,C)-Ph2Pfc}2], where fc stands for ferrocene-1,1ʹ-diyl, with bare or ligand-stabilised group 11 metal ions open an access to diverse oligometallic clusters stabilised by Au-Au, Au-Ag...

Clippane: A Mechanically Interlocked Molecule (MIM) Based on Molecular Tweezers

In this study we report the preparation of a new mechanically interlocked molecule formed by the self-aggregation of two metallotweezers composed by two pyrene-imidazolylidene gold(I) arms and a pyridine-centered pentacyclic bis-alkynyl linker. The mechanically interlocked nature of this molecule arises from the presence of the bulky tert-butyl groups attached to the sides of the pyrene moieties of the arms of the tweezer, which act as stoppers avoiding the dissociation of the self-aggregated metallotweezer dimer once it is formed. By combining experimental techniques, we were able to confirm the mechanically interlocked nature of this molecule in solution, in the gas phase and in the solid state. The behavior of the tert-butyl substituted tweezer differs greatly form that shown by the tweezer lacking of these bulky groups, whose dimeric structure is in equilibrium with the monomeric structure, therefore not showing any mechanical coercion that avoids the disassembly of the self-aggregated structure.

Shape-Adaptability and Redox-Switching Properties of a Di-Gold Metallotweezer

The use of a carbazolyl‐connected di‐gold(I) metallotweezer for the encapsulation of several electron‐poor organic substrates, and a planar Au(III) complex containing a CNC pincer ligand, is described. The binding affinity of the receptor depends on the electron‐deficient character of the planar guest, with larger association constants found for the more electron‐poor guests. The X‐ray diffraction molecular structures of two host:guest adducts show that the host approaches its arms in order to facilitate the optimum interaction with the surface of the planar guests, in a clear example of an guest‐induced fit conformational arrangement. The electrochemical studies of the encapsulation of N,N’‐dimethyl‐naphthalenetetracarboxy diimide (NTCDI) show that the redox active guest is released from the receptor upon one electron reduction, thus constituting an example of redox‐switchable binding.

Guest Encapsulation within Surface-Adsorbed Self-Assembled Cages

Coordination cages encapsulate a wide variety of guests in the solution state. This ability renders them useful for applications such as catalysis and the sequestration of precious materials. A simple and general method for the immobilization of coordination cages on alumina is reported. Cage loadings are quantified via adsorption isotherms and guest displacement assays demonstrate that the adsorbed cages retain the ability to encapsulate and separate guest and non-guest molecules. Finally, a system of two cages, adsorbed on to different regions of alumina, stabilizes and separates a pair of Diels-Alder reagents. The addition of a single competitive guest results in the controlled release of the reagents, thus triggering their reaction. This method of coordination cage immobilization on solid phases is envisaged to be applicable to the extensive library of reported cages, enabling new applications based upon selective solid-phase molecular encapsulation.

Full Visible Spectrum and White Light Emission with a Single, Input-Tunable Organic Fluorophore

The blue emission of M2biQ can be tuned to specific wavelengths throughout the visible region by changing the identity of the cation it interacts with. These optical properties are observed in MeCN solution and the solid state. White light is obtained in MeCN by using either the proper ratio of zinc ions or acid. Thus, M2biQ acts as a nearly universal emitter (λem = 468-690 nm) with large Stokes shifts (116-306 nm, Δν̃ = 7,042-11,823 cm-1). Full spectral profiles as well as quantum yields, lifetimes, and the crystal structures of key RGB and yellow emitters are reported. Emission wavelengths correlate with cationic radius, and TD-DFT calculations show that, for 1:1 complexes, the smaller the ion, the shorter the N-cation bond, and the greater the bathochromic emission shift.

Platinum(ii) non-covalent crosslinkers for supramolecular DNA hydrogels

Manipulation of non-covalent metal–metal interactions allows the fabrication of functional metallosupramolecular structures with diverse supramolecular behaviors. The majority of reported studies are mostly designed and governed by thermodynamics, with very few examples of metallosupramolecular systems exhibiting intriguing kinetics. Here we report a serendipitous finding of platinum(ii) complexes serving as non-covalent crosslinkers for the fabrication of supramolecular DNA hydrogels. Upon mixing the alkynylplatinum(ii) terpyridine complex with double-stranded DNA in aqueous solution, the platinum(ii) complex molecules are found to first stack into columnar phases by metal–metal and π–π interactions, and then the columnar phases that carry multiple positive charges crosslink the negatively charged DNA strands to form supramolecular hydrogels with luminescence properties and excellent processability. Subsequent platinum(ii) intercalation into DNA competes with the metal–metal and π–π interactions at the crosslinking points, switching on the spontaneous gel-to-sol transition. In the case of a chloro (2,6-bis(benzimidazol-2′-yl)pyridine)platinum(ii) complex, with [Pt(bzimpy)Cl]⁺ serving as a non-covalent crosslinker where the metal–metal and π–π interactions outcompete platinum(ii) intercalation, the intercalation-driven gel-to-sol transition pathway is blocked since the gel state is energetically more favorable than the sol state. Interestingly, the ligand exchange reaction of the chloro ligand in [Pt(bzimpy)Cl]⁺ with glutathione (GSH) has endowed the complexes with enhanced hydrophilicity, decreasing the planarity of the complexes, and turning off the metal–metal and π–π interactions at the crosslinking points, leading to GSH-triggered hydrogel dissociation.

We report a serendipitous finding of platinum(ii) complexes serving as non-covalent crosslinkers for the fabrication of supramolecular DNA hydrogels.

Platinum(II) Probes for Sensing Polyelectrolyte Lengths and Architectures

Platinum(II) polypyridine complexes of a square-planar geometry have been used as spectroscopic reporters for quantification of various charged species through non-covalent metal-metal interactions. The characterization of molecular weights and architectures of polyelectrolytes represents a challenging task in polymer science. Here, we report the utilization of platinum(II) complex probes and non-covalent metal-metal interactions for sensing polyelectrolyte lengths and architectures. It is found that the platinum(II) probes can bind to linear polyelectrolytes via electrostatic attractions and give rise to significant spectroscopic changes associated with the formation of metal-metal interactions, and the extent of the spectroscopic changes is found to increase with the lengths of the linear polyelectrolytes. Besides, the platinum(II) probes have been found to co-assemble with the linear polyelectrolytes to form well-defined nanofibers, and the lengths of the linear polyelectrolytes can be directly estimated from the diameter of the nanofibers under transmission electron microscopy observation. Interestingly, upon mixing with the platinum(II) probes, polyelectrolytes with bottlebrush architectures have been found to exhibit larger spectroscopic changes than linear polyelectrolytes with the same chemical composition. Combined with the reported theoretical studies on counterion condensation of polyelectrolytes, the platinum(II) complexes are found to function as spectroscopic probes for sensing the charge densities of the polyelectrolytes with different lengths and diverse architectures. Moreover, platinum(II) probes pre-organized in nanostructured aggregates have been found to intercalate into double-stranded DNA, which are naturally occurring biological polyelectrolytes with helical architectures and intercalation sites, to give significant enhancement of spectroscopic changes when compared to the intercalation of monomeric platinum(II) probes into double-stranded DNA.

Exploiting the labile site in dinuclear [Pd2L2]n+ metallo-cycles: multi-step control over binding affinity without alteration of core host structure

Synthetic metallosupramolecular systems have generally been binary (on/off) when they have control over molecular recognition. This report details a dipalladium(ii) system with four-step graduated control over recognition for a guest.

Amplified circularly polarized phosphorescence from co-assemblies of platinum(ii) complexes

Molecules capable of producing zero-field circularly polarized phosphorescence (CPP) are highly valuable for chiroptoelectronic applications that rely on triplet exciton. However, the paucity of tractable molecular design rules for obtaining CPP emission has inhibited full utilization. We report amplification of CPP by the formation of helical co-assemblies consisting of achiral square planar cycloplatinated complexes and small fractions of homochiral cycloplatinated complexes. The latter has a unique Pfeiffer effect during the formation of superhelical co-assemblies, enabling versatile chiroptical control. Large dissymmetry factors in electronic absorption (g _abs, 0.020) and phosphorescence emission (g _lum, 0.064) are observed from the co-assemblies. These values are two orders of magnitude improved relative to those of individual molecules. In addition, photoluminescence quantum yields (PLQY) also increase by a factor of ten. Our structural, photophysical, and quantum chemical investigations reveal that the chiroptical amplification is attributable to utilization of both the magnetically allowed electronic transition and asymmetric coupling of excitons. The strategy overcomes the trade-off between g _lum and PLQY which has frequently been found for previous molecular emitters of circularly polarized luminescence. It is anticipated that our study will provide new insight into the future research for the exploitation of the full potential of CPP.

Multicomponent Assembled Systems Based on Platinum(II) Terpyridine Complexes

Platinum(II) terpyridine complexes have received tremendous attention in recent years because of their square-planar geometry and fascinating photophysics. Bottom-up self-assembly represents an intriguing approach to construct well-ordered supramolecular architectures with tunable optical and electronic properties. Until now, much effort has been devoted to the fabrication of monocomponent platinum(II) terpyridine-based assemblies. The next step is to develop multicomponent coassembled systems via the combination of platinum(II) terpyridine complexes with other π-organic and -organometallic molecules. The implementation of electron/energy transfer processes renders advanced functionality to the resulting coassemblies. For the fabrication of discrete multicomponent architectures, a feasible protocol is to construct preorganized molecular tweezers and macrocycles with the involvement of platinum(II) terpyridine complexes as the panel units. In view of their planar surface and positively charged character, such supramolecular receptors are capable of encapsulating electron-rich polyaromatic hydrocarbons and organometallic guests via donor-acceptor charge-transfer and/or metal-metal interactions. Intermolecular hydrogen bonds can be further incorporated between the molecular tweezers receptor and the polyaromatic hydrocarbon guests, giving rise to the strengthened binding affinity and sensitive stimuli-responsiveness. On this basis, multilayer donor-acceptor stacks have been obtained via the precise control over the number of pincers, which feature enhanced complexation strength and superior functionality. Moreover, platinum(II) terpyridine-based macrocycles are more suitable for guest accommodation than the corresponding molecular tweezers receptors in light of their definite size and constrained environment. Stimuli-responsive elements can be conveniently implemented into the rigid spacers of the molecular tweezers and macrocyclic receptors, facilitating the capture and release of the sandwiched guests in a highly controlled manner. On the other hand, long-range-ordered supramolecular polymers have been successfully fabricated with linear, hyperbranched, and cross-linked topologies by employing platinum(II) terpyridine-based molecular tweezers/guest recognition motifs as the non-covalent connecting unit. The degree of polymerization of the resulting donor-acceptor-type supramolecular polymers can be efficiently modulated by incorporating intermolecular hydrogen bonds between the molecular tweezers receptor and the complementary guest unit. An alternative approach toward extended multicomponent donor-acceptor assemblies is to mimic the structure of Magnus' green salt. A delicate balance of non-covalent driving forces between homo- and heterocomplexation processes and a deeper understanding of thermodynamic and kinetic behaviors play the decisive roles in the final arrangement of the coassembled structures. Overall, multicomponent coassembly of platinum(II) terpyridine complexes into well-ordered nanostructures would open up a new avenue toward functional supramolecular materials that are especially promising for sensing, optoelectronics, and catalytic applications.

Energy Landscape in Supramolecular Coassembly of Platinum(II) Complexes and Polymers: Morphological Diversity, Transformation, and Dilution Stability of Nanostructures

Establishment of energy landscape has emerged as an efficient pathway for improved understanding and manipulation of both thermodynamic and kinetic behaviors of complicated supramolecular systems. Herein, we report the establishment of energy landscapes of supramolecular coassembly of platinum(II) complexes and polymers, as well as the fabrication of nanostructures with enhanced complexity and intriguing properties from the coassembly systems. In the energy landscape, coassembly at room temperature has been found to only allow the longitudinal growth of platinum(II) complexes and block copolymers into core-shell nanofibers that are the kinetically trapped products. Thermal annealing can switch on the transverse growth of platinum(II) complexes and block copolymers to produce core-shell nanobelts that are the thermodynamically stable nanostructures. The extents of the transverse growth are found to increase with thermal annealing temperatures, leading to nanobelts with larger widths. Besides, rapid quenching of a hot coassembly mixture to room temperature can capture intermediate nanobelt- block-nanofiber nanostructures that are metastable and capable of converting to nanobelts upon further incubation at room temperature. Moreover, sonication treatment has been found to couple with the energy landscape of the coassembly system and open a unique energy-driven pathway to activate the kinetically forbidden nanofiber-to-nanobelt morphological transformation. Furthermore, based on the established energy landscapes, nanosphere- block-nanobelt nanostructures with distinct segmented architectures have been fabricated by thermal annealing of the ternary mixture of platinum(II) complexes, block copolymers, and polymer brushes in a one-pot and single-step procedure. Finally, the nanobelts and nanosphere- block-nanobelt nanostructures are found to possess intriguing morphological stability against acid and dilution, exhibiting characteristics that are important for promising biomedical applications.

Donor-acceptor-type supramolecular polymers on the basis of preorganized molecular tweezers/guest complexation

The bottom-up self-assembly of donor-acceptor (D-A) units has received tremendous attention in recent years. Charge-transfer interactions, which are inherently embedded in D-A pairs, have suffered from some disadvantages such as erratic arrangements and weak binding affinity, thus hampering the precise arrangement of D-A units into long-range-ordered supramolecular polymers. To address this issue, a feasible protocol is to incorporate D-A units into molecular tweezers/guest recognition motifs, which concurrently feature high complexation directionality, strong binding affinity and stimuli-responsiveness. In this tutorial review, we have summarized the recent advances on the tweezering directed formation of D-A-type supramolecular polymers, with particular emphasis on the design principles of monomers and macroscopic behaviors of supramolecular polymers, together with future challenges in this research field.

Modulating Pt⋯Pt metal–metal interactions through conformationally switchable molecular tweezer/guest complexation

Pt(ii)⋯Pt(ii) metal–metal interactions can be modulated for molecular tweezer/guest complexation systems in response to pH variation.